Revert "Add UiThreadTest annotation to ActivityKeyboardShortcutsTest"

This reverts commit 499bb0a2a5c96f797c7041ca6ca89f87bb2d178b.

The change was causing regressions for others, and Things was the only
platform hitting the error it fixed. Things will disable this test
instead as keyboard shortcuts aren't important to its usecase.

Bug: b/67766781
Change-Id: I27b00120806136bdfb8acf8937a49b27b15c134b
1 file changed